Water storage tank with passive enhanced thermal energy management and resistance

ABSTRACT

A water storage tank with passive enhanced thermal energy management is provided. The tank is formed of substantially cylindrical central section comprising a majority of the length along its axis and a dome-shaped section at each end, A first system of managing energy management includes providing insulation covering all or most of the tank in order to prevent heat flow energy leaving the tank. The strength of the insulation, is varied such that one end of the tank has less insulativity than the other end of the tank. Preferably change occurs gradually along the axial length of the tank. The second system for providing passive energy management is using insulation formed of a material that has a glass phase change temperature at or near the temperature of the water when it enters the tank. In order for the temperature of the water in the tank to change from the initial temperature it must first cause the insulation to make that glass phase change in order to either heat up or cool down from its initial temperature point. By varying the mass or thickness of the glass phase insulation along the axial length of the tank the amount of passive energy resistance to change varies thereby causing desired convection currents that serve to maintain a constant temperature within the tank thereby slowing any change of temperature at minimum cost.

BACKGROUND OF THE INVENTION

Tanks used for the storage of elevated temperature water, such ashydronic heating, hot water expansion, buffer tanks, and geothermalheating tanks, are required to maintain a temperature differential withthe outside environment, and in some cases, a temperature gradientwithin the tank itself. The approach to maintaining temperature, ortemperature gradient, has typically been to either insulate the tank asa whole, or actively heat or cool the tank, or a combination of both.Previous approaches to the design of these tanks, including thematerials of construction for fluid barriers, pressure reinforcement,and insulation, have provided largely uniform properties around thetank, not taking advantage of differences in thermal properties of thesematerials to optimize the performance of the tank. Meanwhile, activeheating and cooling has the disadvantage of consuming additional energy,usually in the form of electricity, natural gas, or other fossil fuels.Therefore, there is a need for novel hot water storage tanks that takeadvantage of differences in the thermal properties of the materials ofconstruction to provide enhancements in passive thermal management.

GENERAL DESCRIPTION OF THE INVENTION

The present invention provides an efficient, inexpensive passive meansto provide a double diaphragm water tank, capable of providing thedesired temperature maintenance. In accordance with one preferred aspectof the present invention, there is provided a double diaphragm holdingtank with passive thermal management for the storage of water attemperatures up to 250° F. This invention avoids the use of more costlyactive heating or cooling means. Preferably, the tank comprises acentral, elongated, substantially cylindrical housing section 1, joinedat two circumferential end locations 2 and 22 to an upper and a lowerdome-shaped housing end-sections. Within the tank housing sections, andsecured to the inner circumferential surface of the cylindrical housingsection is a flexible diaphragm and, preferably, a rigid diaphragm. Theflexible diaphragm is preferably secured to the upper circumferentialrim of the rigid diaphragm, which in this preferred embodiment issecured to the inner surface of the central housing section and theflexible diaphragm is sealingly secured to the upper rim, andcircumferentially internally of, the rigid diaphragm by a removablecircumferential clip. This invention provides an insulation layersurrounding the housing sections, which is preferably formed on theelongated central tank section and at least closely adjacent the domesections, if present. Operatively connected to the bottom of the tankand extending through the bottom of the rigid diaphragm, if present, isa water inlet pipe, and operatively connected to and extending throughthe top of the tank is a pressure relief valve and nipple.

This invention provides a varying insulative effectiveness of theinsulation layer along the length of at least the central elongatedsection, so that either the upper or lower dome-shaped housing sectionis covered with a less effective insulation layer, so that an internaltemperature gradient is formed in the water, and thus to createconvective mixing currents in water within the tank, when the water isat a temperature different from the temperature exterior of the tank.This can be accomplished by varying the thickness of the insulationalong its length, or to otherwise change the effectiveness of theinsulation, such as by changing its nature.

Another novel aspect of this invention is the use of an insulativematerial that has a glass phase transition temperature (t_(g)) of aboutthe incoming temperature of the water in the tank, or preferablyslightly lower. This temperature is commonly up to about 250° C.Generally, the insulation material should be tailored to the intendeduse of the tank, i.e., for holding cool water at room temperature orlower, or to hold hot water, as may be used for a hot water tank in thehome or commercial building or factory.

Further, the desired variability of the insulative effectiveness can beachieved by selecting insulation material having a t_(g) near thedesired temperature of the water in the tank.

The insulative effectiveness of material selected for its t_(g) may alsobe varied by varying the thickness of the glass phase insulation, or byreducing the percentage of that material in the total insulation, alongthe axial length of the tank, or even by varying the nature of theinsulation material, so as to reduce the t_(g) of material forming theinsulation along the length of the tank, to thereby create differenttemperatures along the length of the tank, so as to create the desiredconvection currents.

The glass phase transition temperature can also be useful when it isdesired to merely increase the time of maintaining a constanttemperature as compared with using the usual selection of materialhaving a higher t_(g). glass phase transition temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-section of an elevated temperature watertank according to an embodiment of the invention, representing the tankcharged with air pressure and the space below the flexible diaphragmbeing not charged of water; and

FIG. 1B is an expanded view of the schematic cross-section of thediaphragm tank in FIG. 1.

DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS

FIG. 1 is a cross section of a double diaphragm tank 11 with passivethermal management.

The upper portion of inside the tank, outside of the rigid diaphragm 31,and flexible diaphragm 32, is charged with air through the nipple 9, andlower portion, between rigid diaphragm 31 and flexible diaphragm 32, maybe charged with water. The tank comprises a central, substantiallycylindrical housing section 1, joined at two circumferential jointlocations 2 and 22 to dome-shaped housing sections 5 and 6,respectively. The overall tank 11, preferably forms a substantiallyisotensoidal shape. The dome-shaped section 5 further comprises an airvalve and nipple 9, which allows one area of the tank to be charged withair or gas. The lower dome-shaped section 6 further comprises a threadedconnection 10 through which water can flow, via pipe 110, which extendsto the bottom of the rigid diaphragm 31; through a water-tight seal thepipe 110 can discharges water into the volume between the two diaphragms31,32. The condition of the flexible diaphragm 32, when the volume isfilled with water is shown by the dashed line A, in FIG. 1.

The three housing sections 1, 5, and 6 are further reinforced with apressure barrier, 41, and an insulation layer 42, and an outer shell,43, substantially surrounding the pressure barrier 41, with openings foran inlet/outlet line 10 and for the pressure relief valve 9, and anyother fittings or valve. Although the insulation layer 42 is shown as arectangular box surrounding the tank, the insulation layer 42 isactually formed adjacent to at least the cylindrical central section 1,as shown in FIG. 1B.

In certain embodiments, the tank sections and housing sections 1, 5, 6and rigid diaphragm 31, may be independently, or together formed ofnon-metallic materials, selected from the group including thermoplasticpolymers, thermoset polymers, whether plastic or elastomeric, naturalrubbers, or multilayer materials comprising the same.

In certain embodiments, the tank segments and housing sections 1, 5, 6and rigid diaphragm 31 may be formed of materials selected from a groupof thermoplastics including polyolefins, polyethylene, polypropylene,polybutylene, nylon, PVC, CPVC, ionomers, fluoropolymers, copolymers,crosslinked polyolefins such as crosslinked polyethylene (PEX, PEX-a.PEX-b, PEX-c or XLPE), or multilayer structures comprising the same. Theindividual items forming the above-described tank: housing sections 1,5, 6 and rigid diaphragm 3 may also include a “tie-layer”. A “tie layer”is usually one or a combination of two or more mutually compatiblematerials that form a bonding layer between two mutually incompatiblematerials. Tie layers may include, for example, a thermoplastic materialthat provides adhesion to two adjacent materials, most often throughmelt processing or chemical reactions; modified acrylic acid, oranhydride grafted polymers or those similar to but not limited toDuPont's Bynel, Nucrel, and Fusabond grades, or those described andreferenced, as further examples, in U.S. Pat. Nos. 8,076,000, 7,807,013and 7,285,333. The melting point or melt index of the tie layer may beselected so that the tie-layer can be post-processed withoutsubstantially melting or flowing other non-metallics in the structure.

In some embodiments, housing sections 1, 5, 6 and rigid diaphragm 31 maybe filled polymers or comprise solids such as but not limited toparticles or flakes of polymers or minerals including glass, talc,carbon and graphite; chopped fibers, discontinuous fibers, short or longfibers, or continuous fibers of polymers or minerals including glass orcarbon; nanocomposites; clays; or other fibers, particles, flakes orhollow microspheres. In some embodiments, housing sections 1, 5, 6 andrigid diaphragm 31 are independently or together metals, such as but notlimited to steels, stainless steels, aluminum, or the like. In somecases, 5 and 6 may further comprise fittings or valves, including thosemade of metals or non-metals, including but not limited to threadedfittings, compression fittings, bulkhead fittings, quick-disconnectfittings, clip or crimp fittings, air valves, ball valves, needle valvesor the like. In some cases, housing sections 5 and 6 may providesurfaces on which to make additional connections through processesincluding but not limited to stick welding, butt welding, spin welding,friction stir welding, ultrasonic welding, induction welding, solventwelding, RF/microwave processing, resistance-based fusion, adhesives,tie layers, or the like. These fittings, valves, or other surfaces maybe connected by means known to those skilled in the art to additionalsystem components including, but not limited to, heaters, filters,pumps, pipes, tanks, or hoses.

In certain preferred embodiments, housing sections 1, 5, 6 and rigiddiaphragm 31 are polypropylene, ethylene-polypropylene copolymers, andglass particle or glass fiber-filled polypropylene andethylene-polypropylene copolymers. The ethylene-propylene copolymers maybe block copolymers. The melting point and melt index of housingsections 1, 5, 6 and rigid diaphragm 31 may be tailored to improve theassembly and processing of the tank. In certain embodiments, the outersurface of housing sections 1, 5, 6 and rigid diaphragm 31 may beindependently or together surface modified by high energy treatmentsincluding ion implantation, plasma, corona or arc, to improve adhesionto adjacent materials. The inner surface of housing sections 1, 5, 6 andrigid diaphragm 31, and flexible diaphragm 32, can also be modified tochange properties, such as, but not limited to, chemical resistance,permeability, and wettability by water. Treatments may include but notlimited to fluorination or the technologies employed by NBD Nano, or bymetallization through chemical vapor deposition or the like. In certainpreferred embodiments, polypropylene, polypropylene copolymers, glassfilled polypropylene and glass filled polypropylene copolymers aretreated by a flame to improve adhesion to adjacent layers. In somepreferred embodiments, housing sections 1, 5, 6 and rigid diaphragm 31,and flexible diaphragm 32 may include antimicrobials, includingantifungals, antivirals, or antibiotics, or comprise silver. In otherpreferred embodiments, housing sections 1, 5, 6 and rigid diaphragm 31,and flexible diaphragm 32 contain antioxidants and stabilizers.

The flexible diaphragm 32 may be comprised of a polymer, elastomer,rubber, RTV, or thermoplastic, or multiple layers comprising the same.In certain preferred embodiments, the diaphragm 32 comprises butylrubber or EPDM. In other embodiments, the diaphragm may be filled withsolids such as but not limited to particles or flakes of polymers orminerals including glass, talc, carbon and graphite; chopped fibers,discontinuous fibers, short or long fibers, or continuous fibers ofpolymers or minerals including glass or carbon; nanocomposites; clays;or other fibers, particles, flakes or hollow microspheres; or woven ornon-woven fabrics; to improve the thermomechanical properties ordecrease permeability of gases through the membrane. In someembodiments, these multiple layers of the diaphragm are bonded, but thelayers may also be non-bonded. In certain embodiments, the layersinclude a thin higher modulus layer supported by a thicker, lowermodulus layer. The high modulus layer may be selected from chemicallyresistant polymers, or polymers preferred for contact with potablewater, such as polypropylene, polyethylene, polybutylene, or the like.The low modulus layer may be selected for different properties, such asdurability, toughness, and low cost, protected from contact with thepotable water by the high modulus layer.

The flexible diaphragm 32 may also comprise features to reduce thetendency of the diaphragm to wear or become fatigued in service, orprotect it from abrasion or cutting by adjacent structures such as aclinch ring. In some cases, the flexible diaphragm 32 may be ofsubstantially non-uniform thickness or modulus. The non-uniformthickness or modulus may be controlled across the surface to reduce thetendency for the diaphragm to rub against itself, against otherstructures, abrade or tear. The flexible diaphragm 32 can also besubstantially folded, in an accordion, serpentine, or wavy shape. Theseshapes may allow for more compact or rigid diaphragms to be used, whilestill allowing extension in service without localized strains exceedingthe limits of the materials. The diaphragm may be further molded orinstalled in the shape or orientation that it is most often in serviceto reduce the in-situ strains or abrasion.

The flexible diaphragm 32 can be sealably joined at the peripheral edgeto the rigid diaphragm 31, by methods known to those skilled in the art.Such sealable joints can be formed using, for example, adhesives,solvent bonding, stick welding, butt welding, spin welding, frictionstir welding, induction welding, RF/microwave processing,resistance-based fusion, tie layers, or the like, with or withoutadditional sealants. In certain preferred embodiments, the connection ofthe peripheral edges of diaphragms 31 and 32 may also be made by theapplication of a rigid clinch ring 3. Such a clinch ring 3 can becomprised of metal or non-metal and provides a clamping force by meansknown to those skilled in the art, such as but not limited to crimping,snap coupling, fasteners, adhesives, melt processing, thermoforming orthe like. The connection between clinch ring 3, the flexible diaphragm32 and the rigid diaphragm 31 is accomplished by the use of features orstructures that improve the connection and seal such as lips, dimples,ridges, knobs, integral rings, including multiple rings.

In certain preferred embodiments, the flexible diaphragm 32 may extendover both sides of the rigid diaphragm 31 and/or be gripped between thesurfaces of a u-shaped clinch ring 3, i.e., a preferably elastic ringwith a u-shaped cross-section. In some cases, the clinch ring 3 may havea contour that controls the radius of curvature of the diaphragm andprotects the diaphragm from contacting any sharp edges.

In some embodiments, housing sections 1, 5, 6 may be further reinforcedby the pressure barrier 41 to increase the pressure carryingcapabilities of the expansion tank. This reinforcement may compriseglass (including but not limited to borosilicate, e-, s-, and cr-glass),basalt, quartz, carbon or other inorganic or mineral fibers. Thereinforcement may also comprise organic or inorganic polymer fibers suchas but not limited to polyester, nylon, polypropylene, aramid, Kevlar,Nomex, PPS or carbon. These fibers or fillers may be continuous ordiscontinuous fibers, chopped, non-wovens or random oriented mat, or maybe in the form of fiber tapes. The reinforcing materials may be in athermoset or thermoplastic matrix, or present without a matrix. Incertain preferred embodiments, the reinforcement is afiberglass-reinforced epoxy. The reinforcement of pressure vessels by,for example, filament winding is well known to those skilled in the art.In some cases, the reinforcement is a metal such as but not limited tosteels, stainless steels, aluminum or the like.

In certain embodiments, the tank does not include a rigid or flexiblediaphragm, but is rather largely filled with water. In other preferredembodiments, there may be additional ports into the tank, includingthrough the wall of the cylinder 1 and the pressure barrier 41. Incertain embodiments, dome 5 may include additional features thatencourage mixing or turbulent flow, or in some cases, laminar flow. Inother embodiments additional features or plumbing may extend fromfitting 10 into the water chamber to control flow of water within thetank.

In some embodiments, housing sections 1, 5, 6 with or without rigiddiaphragm 31 and flexible diaphragm 32, and with or without pressurebarrier 41, can be further insulated with insulation layer 42. Theinsulation layer 42 may be material with a low K value, includingcontinuous or discontinuous fiber insulation, pulverized or aeratedmaterials, flakes, or chopped materials that are poured or blown into anouter shell 43, or may be wet blown onto the surface with or without theuse of binders or adhesives. The insulation layer 42 may also be aflexible, rigid, or semi-rigid foam. Although the insulation layer 42and outer shell 43 are diagrammatically shown as a rectangle, they arepreferably formed concentric with the pressure barrier 41. The foam maybe comprised of polymers, thermosets, elastomers, ceramics, or the like.The foam may further comprise air, CO2, or blowing agents includinghydrofluorocarbons. The foam may be formed by pouring a foamingmaterial, such as a two-part expanding foam urethane, into the 43.Alternatively, preformed foam can be wrapped around the tank or joinedas sections such as in a “clam shell”. Some foams, including flexible,semi-rigid, heat formable, or kerfed may be wrapped around the tank. Insome preferred embodiments, there is a small gap between the pressurebarrier 41 and the insulation layer 42.

The outer shell 43 can be comprised of metal or non-metals, includingthermoplastics or thermosets. It may be formed as a continuous shell bymeans such as but not limited to extrusion or rotomolding or it may beapplied as a wrap. The wrap may be joined by overlap joints, but welds,seam welds, or mechanical fasteners; the mechanical fasteners mayfurther engage the insulation layer 42. Outer shell 43 may also have thetendency to shrink by either induced stress from the fabricationprocess, application of additional heat (such as heat shrink), or by theelasticity of outer shell 43. In a preferred embodiment, there is asmall gap between the outer shell 43 and the insulation 42. Insulationlayer 42 may be non-uniform around the tank. In one preferredembodiment, there is extra insulation on the top of the tank, and lessor no insulation at the bottom. The pressure barrier 41, insulationlayer 42 and outer shell 43 may also include barrier layers, such asplastic or elastomeric moisture barriers, thermally reflective foils,metallized layers, or the like. In one preferred embodiment, insulationlayer 42 and outer shell 43 may each independently have a reflectivelining 50, such as shown in FIG. 1B.

All of these materials and design elements are well known to thoseskilled in the art and are common in the industry. The novel invention,disclosed herein, is the use of novel passive designs to enhance thethermal management without the use of active heating or cooling,specifically for applications where the temperatures exceed about 65° C.

Smart Mixing

In one embodiment of Smart Mixing, a tank shown in FIG. 1 is capable ofoperating from −40° F. to a maximum temperature 150-250° F. The tankcomprises a dome 5, fiber reinforcement 41, insulation layer 42, andouter shell 43, that independently or together produce a K value that isat least 10% higher through the dome 5, than the rest of the shell, ormore preferably at least 25% higher. This decreased insulation at thetop of the tank changes the near-field temperature of the fluid inside.The temperature differential between the top surface of the tank and therest of the fluid in the tank has been found to induce convectivecurrents, which stir the fluids, improving the temperature distributionas well as cleaning the surfaces from fouling, all without anyadditional added forces, stirrers, or heaters. Similarly, the SmartMixing tank can have a lower dome 6, fiber reinforcement, bottominsulation, or other features which produce a K value that is 10%-25%lower than the rest of the shell, causing near-field temperatureinversion, increasing convection within the tank and stirring thesediment from the bottom of the tank, without the need for additionalmoving parts or energy inputs.

In another embodiment of Smart Mixing, a multi-layer composite tank iscapable of operating from −40° F. to a maximum temperature 150-250° F.The inner surfaces of housing sections 1, 5, 6 are manufactured withinternal upsets. These upsets, or small baffles, may be as large as 0.1″or as small as 0.05″, protruding into the inside of the tank, such thatwhen fluids are moving within the tank, either from bulk or fromconvective currents, the flow is disrupted and the increase inturbulence improves the mixing within the tank and cleaning of surfaceswithout the need for additional moving parts or energy inputs.

Smart Strain Relief

In another embodiment of the improved passive thermal management, a tankshown in FIG. 1 is capable of operating from −40° F. to a maximumtemperature 150-250° F., and is fitted with additional ports through theside wall. Ports or openings that penetrate the outer wall of the tank,especially through housing section 1 and pressure barrier 41, are wellunderstood to be weak points in the structure of the tank, and thelocation of stress risers. These areas of weakness and enhanced stressare further exacerbated by temperature differentials with the outsideenvironment. In this embodiment, metal is incorporated in and aroundports. This serves to draw temperature from the tank, into the ports,and moderate the temperature transition between the tank and the outsideenvironment and reduce thermal stress on the sensitive joint structures,without the need for additional fiber reinforcement.

Phase Transition Materials

In another embodiment of the novel passive, integrated thermalmanagement of the present invention, a multi-layer composite tank shownin FIG. 1 is capable of operating from as low as −40° F. to a maximumtemperature 150-250° F. and the thermal management is imparted to saidtank through the use of selected phase transition materials asinsulators. Phase transition materials may include thermoplastics orthermosets that have a glass transition temperature within the operatingwindow of said tank, preferably at or below the initial inlettemperature of the water entering the tank. These phase transitionmaterials are used to maintain the stored water temperature near thephase transition for longer than if the phase transition was outside,especially far above, the water temperature.

Examples of polymers that could be used to prepare insulation are shownin the several listed in Table 1, below, together with their glass phasetransition temperatures (t_(g)). There are many well-known textsproviding the transition temperatures of available synthetic polymers aswell as natural materials.

TABLE I Tg Polymer (Glass Transition Temperature) Nylon 6/6 50° to 60°C. Polycarbonate 140° to 150° C. Polyethelene Terephthalate (PET) 70° to80° C. Polymethyl Methacrylate (PMMA) 85° to 105° C. PolyphenyleneSulfide 85° to 95° C. Polystyrene 90° to 110° C. Polytetrafluoroethylene(PTFE) 120° to 130° C. Polyeurethane (Thermoplastic) 120° to 160° C.Polyvinyl Alcohol 80° to 90° C. Polyvinyl Chloride (PVC) 65° to 85° C.Ranges of temperatures are often shown due to the fact that such valuesare often dependent upon the particular molecular weight of the polymer,its method of manufacture and many factors well-known to the polymerchemists who prepare such materials. The novelty of the presentinvention does not reside in the method of making the polymers, butrather in the novel way in which they are being used to maintaintemperatures of stored water, especially hot water. Other polymers maybe used for purposes of this invention without departing from its scope.The listed Tg is usually some middle point within the range over whichthe polymer transitions from a softer state to a rigid glass. Therefore,it should be understood that the phase change effect on temperature maylinger over a range of dropping temperatures.

Air Gap Inducers

In one embodiment of integrated passive thermal management, amulti-layer composite tank in FIG. 1 is capable of operating from −40°F. to a maximum temperature 150-250° F. Novel features imparted into thewall of housing section 1, pressure barrier 41, insulation layer 42, andouter shell 43 intentionally provide spacing between the two layers. Inone preferred embodiment, the tank includes air gap inducers 51. Thesestand-offs are designed to create small, air filled spaces betweenpressure barrier 41 and insulation layer 42, and between insulationlayer 42 and outer shell 43. In one exemplary embodiment, thesestand-off inducers decreased the heat loss from the tank by 20%. Inanother embodiment multiple air gaps are used. These air gaps can beindividually selected between the rigid diaphragm 31 and dome 6; housingsections 1, 5, 6 and the pressure barrier 41; the pressure barrier 41and the insulation layer 42; and the insulation layer 42 and the outershell 43.

These air gap inducers have been found to maintain the temperature ofthe tank for 2× longer without the need for additional heat input. Inone preferred embodiment, the air gap is greater at the top than at thebottom to optimize temperature striation, ideally suited forapplications such as solar hot water storage tanks.

In another embodiment, the air gap between surfaces is controlled bychanging the internal pressure or modulus of the materials ofconstruction during the curing of the matrix of pressure barrier 41. Ina preferred embodiment, the modulus of the housing sections 1, 5, 6, isdecreased by 5% or more through the use of temperature and the internalair pressure is increased by at least 10%. By increasing the airpressure inside the tank, and decreasing the modulus of the innerlayers, the gap between layers can be reduced to less than 0.01 whichhas been found to be optimal for passive thermal management.

In another embodiment, the thermal management of the tank controlled bytailoring the amount of thermoset matrix, or fiber volume fraction, inthe tank. In one preferred embodiment, the matrix is an epoxy, thefibers are glass, and the relative concentration of the epoxy is loweron the top of the tank than on the bottom. In another preferredembodiment, the amount of epoxy is below the amount theoretically neededto fill the spaces between the fibers resulting in extremely small voidswhich help serve to insulate the tanks and retain heat.

In another embodiment, a small air gap is provided to said tank byreducing the bonding between the housing sections 1, 5, 6 to thepressure reinforcement at joints 2 and 22. This reduces the heat loss atthis location, increasing the temperature and reducing the modulus atjoints 2 and 22 to improve the ductility and toughness in this highstress location. This air gap is most effective if maintained at roughly1″ wide and less than 0.05″ h.

In some preferred embodiments, the rigid and flexible diaphragms 31 and32, domes 5, 6, or the cylinder 1, may include layers that serve toreduce heat transfer, including reflective layers, such as metalizedlayers, or may be light in color to reduce the amount of radiative heatloss.

Smart Susceptors

In one embodiment of integrated thermal management, a multi-layercomposite tank is capable of operating from −40° F. to a maximumtemperature 150-250° F. A susceptor such as carbon, graphite, or metalis added to housing sections 1, 5, 6 so that it may be heated from anexternal energy source such as induction, RF, or microwave, withoutsignificantly heating the insulation or fiber reinforcement. In anotherembodiment, ports in and out of the tank comprise metals which may beheated by said external power supplies.

What is claimed is:
 1. A double diaphragm tank with passive thermalmanagement for the storage of water at temperatures up to 150° C., whileavoiding the use of active heating or cooling means, the tank comprisinga central, substantially cylindrical housing section 1, joined at twocircumferential locations 2 and 22 to an upper and a lower dome-shapedhousing sections, and within the tank housing sections, and secured tothe inner circumferential surface of the cylindrical housing section isa rigid diaphragm, and a flexible diaphragm, the upper circumferentialrim of the rigid diaphragm being secured to the inner surface of thecentral housing section and the flexible diaphragm being sealinglysecured to the upper rim, and circumferentially, internally of the rigiddiaphragm, by a removable circumferential clip; and an insulation layersurrounding the housing sections; there being operatively connected tothe bottom of the tank, and extending through the bottom of the rigiddiaphragm, a water inlet pipe; and operatively connected to andextending through the top of the tank is a pressure relief valve; theimprovement comprising, varying the insulative effectiveness of theinsulation layer, axially along the central housing section 1, so thatthe either the upper or lower dome-shaped housing sections are coveredwith a less effective insulation layer, so as to create an internaltemperature gradient in any water held in the tank, so as to createconvective mixing currents in such water within the tank, when the wateris at a temperature different from the ambient temperature exterior ofthe tank.
 2. The double diaphragm tank of claim 1, wherein theinsulative effectiveness of the insulation layer is varied by providinga sealed insulation and varying the width of the air gaps withinportions of the insulation layer.
 3. The double diaphragm tank of claim1, wherein the insulative effectiveness of the insulation layer isvaried by changing the thickness of the insulation layer.
 4. The doublediaphragm tank of claim 1, extending vertically, wherein the insulativeeffectiveness of the insulation layer is varied such that the Kvalue ofthe insulation layer in one of the upper or lower dome sections is atleast 10% greater than the insulation in the rest of the tank, intendedto create convective currents in water in the tank to improvetemperature distribution in the water and to prevent fouling of theinternal surfaces of the tank.
 5. A double diaphragm tank with passivethermal management for the storage of water at temperatures up to 250°F., while avoiding the use of active heating or cooling means, the tankcomprising a central, substantially cylindrical housing section 1,joined at two circumferential locations 2 and 22 to an upper and a lowerdome-shaped housing sections, and within the tank housing sections, andsecured to the inner circumferential surface of the cylindrical housingsection is a rigid diaphragm, and a flexible diaphragm, the uppercircumferential rim of the rigid diaphragm being secured to the innersurface of the central housing section and the flexible diaphragm beingsealingly secured to the upper rim, and circumferentially internally of,the rigid diaphragm by a removable circumferential clip; and aninsulation layer surrounding the housing sections; there beingoperatively connected to the bottom of the tank and extending throughthe bottom of the rigid diaphragm is a water inlet pipe, and operativelyconnected to and extending through the top of the tank is a pressurerelief valve; the improvement comprising securing to the housingsections a layer of insulating material having a glass transitiontemperature not greater than the desired temperature of the water in thetank, in order to maintain the temperature of the tank near the glasstransition temperature.
 6. The double diaphragm tank of claim 4, whereinthe insulative effectiveness of the insulation layer is varied byvarying the quantity of the glass phase transition material within theinsulation layer.
 7. The double diaphragm tank of claim 4, wherein theinsulative effectiveness of the insulation layer is varied by varyingthe thickness of the glass phase transition material within theinsulation layer.
 8. The double diaphragm tank of claim 4, wherein theinsulative effectiveness of the insulation layer is varied by varyingthe spacing of the glass phase transition material insulation layer fromthe surface of the tank shell.